title: Potential of magnetic resonance-guided focused ultrasound for intracranial hemorrhage: an in vitro feasibility study.
abstract: BACKGROUND
  Intracranial hemorrhage has a mortality rate of up to 40-60% due to the lack of effective treatment. Magnetic resonance-guided focused ultrasound may offer a breakthrough noninvasive technology, by allowing accurate delivery of focused ultrasound, under the guidance of real-time magnetic resonance imaging.
  
  
  OBJECTIVE
  The purpose of the current study was to optimize the acoustic parameters of magnetic resonance-guided focused ultrasound for effective clot liquefaction, in order to evaluate the feasibility of magnetic resonance-guided focused ultrasound for thrombolysis.
  
  
  METHODS
  Body (1·1 MHz) and brain (220 kHz) magnetic resonance-guided focused ultrasound systems (InSightec Ltd, Tirat Carmel, Israel) were used to treat tube-like (4 cc), round (10 cc), and bulk (300 cc) porcine blood clots in vitro, using burst sonications of one-second to five-seconds, a duty cycle of 5-50%, and peak acoustic powers between 600 and 1200 W. Liquefied volumes were measured as hyperintense regions on T2-weighted magnetic resonance images for body unit sonications (duration of one-second, duty cycle of 10%, and power of 500-1200 W). Liquefaction efficiency was calculated for brain unit sonications (duration of one-second, duty cycle of 10%, power of 600 W, and burst length between 0·1 ms and 100 ms).
  
  
  RESULTS
  Liquified lesion volume increased as power was raised, without a thermal rise. For brain unit sonications, a power setting of 600 W and ultrashort sonications (burst length between 0·1 and 1·0 ms) resulted in liquefaction efficacy above 50%, while longer burst duration yielded lower efficacy.
  
  
  CONCLUSIONS
  These results demonstrate the feasibility of obtaining reproducible, rapid, efficient, and accurate blood clot lysis using the magnetic resonance-guided focused ultrasound system. Further in vivo studies are needed to validate the feasibility of magnetic resonance-guided focused ultrasound as a treatment modality for intracranial hemorrhage.
authors.affiliation: Department of Neurosurgery, Sheba Medical Center, Tel-Hashomer, Israel.
authors.forename: Sagi
authors.initials: S
authors.lastname: Harnof
authors.forename: Arik
authors.initials: A
authors.lastname: Hananel
authors.forename: Zion
authors.initials: Z
authors.lastname: Zilby
authors.forename: Iris
authors.initials: I
authors.lastname: Kulbatski
authors.forename: Moshe
authors.initials: M
authors.lastname: Hadani
authors.forename: Neal
authors.initials: N
authors.lastname: Kassell
mesh_terms: D000818:Animals; D005240:Feasibility Studies; D020300:Intracranial Hemorrhages / Q000000981:diagnostic imaging*; D008279:Magnetic Resonance Imaging / Q000379:methods; D061185:Mechanical Thrombolysis / Q000379:methods*; D025321:Surgery, Computer-Assisted / Q000379:methods*; D013552:Swine; D014463:Ultrasonography
keywords: intracranial hemorrhage; magnetic resonance-guided focused ultrasound; noninvasive; stroke; thrombolysis